Mongo aggregation query to calculate multiple computed values - mongodb

Question

Given the below documents.
{
_id: 1,
ExpirationDate: ISODate("2017-05-02T09:29:46.006+0000")
}
{
_id: 2,
ExpirationDate: ISODate("2017-05-12T09:29:46.006+0000")
}
{
_id: 3,
ExpirationDate: ISODate("2017-05-23T09:29:46.006+0000")
}
How can I use aggregation pipleline to compute the following output?
{
"NumberOfSubscriptionExpiringToday": 12,
"NumberOfSubscriptionExpiringWithInAWeek": 4
}
I am looking to accomplish this with just one query instead of two. Here is what I have so far...
.aggregate([
{
$match: {
"ExpirationDate": {
$gte: ISODate("2017-05-02T00:00:00.000+0000"),
$lte: ISODate("2017-05-03T00:00:00.000+0000")
}
}
},
{
$project: {
_id: 1
}
},
{
$count: "ExpiringToday"
}
]);
.aggregate([
{
$match: {
"ExpirationDate": {
$gte: ISODate("2017-05-02T00:00:00.000+0000"),
$lte: ISODate("2017-05-08T00:00:00.000+0000")
}
}
},
{
$project: {
_id: 1
}
},
{
$count: "ExpiringInSevenDays"
}
]);

Answer 1

You can do it in single aggregation query with $cond operator to check if each document expiration date falls into [today, tomorrow) range, or in [tomorrow, weekAfterToday) range:
var today = ISODate("2017-05-04T00:00:00.000");
var tomorrow = ISODate("2017-05-05T00:00:00.000");
var weekAfterToday = ISODate("2017-05-11T00:00:00.000");
db.collection.aggregate([
{ $match: { "ExpirationDate": { $gte: today, $lt: weekAfterToday }}},
{
$project: {
ExpiringToday: {
$cond: {
if: {
$and: [
{$gte: ["$ExpirationDate",today]},
{$lt:["$ExpirationDate",tomorrow]}
]
}, then: 1, else: 0
}
},
ExpiringInAWeek: {
$cond: { if: {$gte: ["$ExpirationDate",tomorrow]}, then: 1, else: 0 }
}
}
},
{ $group: {
_id: 1,
NumberOfSubscriptionExpiringToday: {$sum: "$ExpiringToday" },
NumberOfSubscriptionExpiringWithInAWeek: {$sum: "$ExpiringInAWeek" }
}
},
{ $project: { _id: 0 }}
]);
Consider also to make two simple requests:
var numberOfSubscriptionExpiringToday = db.collection.count(
{ "ExpirationDate": { $gte: today, $lt: tomorrow }}
);
var numberOfSubscriptionExpiringWithInAWeek = db.collection.count(
{ "ExpirationDate": { $gte: tomorrow , $lt: weekAfterToday }}
);